Donald Trump's rivals are about to be tested in another cluster of elections

Donald Trump. Benjamin Krain/Getty Images Another group of primaries and caucuses on Saturday will provide the first test for Donald Trump's GOP rivals to try and halt his momentum after the "Super Tuesday" elections earlier this week.

Three states are hosting Republican caucuses Saturday morning and afternoon: Kansas, Kentucky, and Maine. Another state, Louisiana, is holding a traditional primary election all day.

Trump has become such an undisputed frontrunner in the primary that anti-Trump agitators are increasingly hoping to defeat him at the Republican convention this summer. If Trump doesn't secure an outright majority of the convention delegates, Trump's critics propose, then the non-Trump delegates could form a coalition against him.

But for even that scenario to unfold, Rubio or Cruz are going to have to perform markedly better in the upcoming contests. A fourth Republican candidate, Ohio Gov. John Kasich, could also face increasing calls for him to drop out if he continues to slog behind on Saturday.

Trump has done better in primaries than in caucuses so far, so Saturday's caucus-heavy contests could provide an opportunity for the billionaire's opponents to chip away at his lead. Caucuses require voters to show up at a certain time and stay for a relatively lengthy process, so far fewer voters participate and better-organized campaigns have the advantage.

But Trump could also be expected to do quite well on Saturday: He has defeated his rivals in states similar to Kentucky and Louisiana, and he has done quite well in New England, where the Maine caucuses will be held. Additionally, Trump was recently endorsed by Maine Gov. Paul LePage.

The two Democratic presidential candidates, Hillary Clinton and Bernie Sanders, are also set to face off Saturday in Kansas, Louisiana, and Nebraska.